Not recommended. With the red triangle on and P0A93 stored, limp only as far as needed to stop safely; continuing to drive risks overheating and damaging the inverter. P0A93 is a hybrid powertrain code: the inverter's dedicated cooling loop isn't moving enough coolant to keep the power electronics cool, so the hybrid control system logs the fault and usually lights the red triangle warning alongside the check-engine light. On the Toyota Prius - by far the most common vehicle to set it - the usual culprit is a worn-out electric inverter coolant pump, often together with trapped air or old coolant in the loop. It tends to show up in hot weather or after the car has been working hard, and may drop the car into reduced power. Because an overheating inverter can be damaged, this is one to address quickly rather than drive on.
What P0A93 means
A hybrid's inverter and motor-generator electronics run their own coolant circuit, completely separate from the engine's cooling system, and that circuit is pushed around by a small electric water pump rather than a belt-driven one. The hybrid control computer watches how the inverter coolant temperature responds; if cooling performance falls short of what it expects - the temperature climbing when it shouldn't, or never stabilising - it sets P0A93, frequently paired with Toyota's Information Code 346. The code describes insufficient cooling, not one specific part, so the job is to find why flow or heat transfer is inadequate: a pump that no longer moves coolant properly, air that has collected in the loop, or coolant that is low or past its service life.
Symptoms
- Red triangle master warning light, usually with the check-engine light
- Hybrid system warning with reduced power or 'limp' mode
- Often appears in hot weather or after hard driving, and may ease once the car cools
- Companion Information Code 346 stored in Toyota scan data
- In severe cases the pump shorts internally - smoke, or a blown AM2 fuse
Common causes
- Worn or seized electric inverter coolant pump - the dominant cause, especially on 2004-2009 (Gen 2) Prius, though every generation uses this pump
- Air pocket trapped in the inverter coolant loop - common after any coolant work and the subject of Toyota TSB EG001-07
- Low or degraded inverter coolant - the pink Toyota long-life coolant breaks down over time or drops from a slow leak
- Restricted or blocked inverter radiator reducing heat transfer
- Less often, a faulty coolant temperature sensor or damage to the inverter assembly itself
Severity & driving advice
Severity: High — An inverter that overheats can be damaged, and that repair is expensive - treat a red-triangle P0A93 as drive-only-to-safety.
Can I drive? Not recommended. With the red triangle on and P0A93 stored, limp only as far as needed to stop safely; continuing to drive risks overheating and damaging the inverter.
Diagnostic approach
- Scan for codes and freeze frame — Confirm P0A93, note Toyota Information Code 346, and record the conditions when it set - hot weather and high load are typical - plus any companion hybrid codes.
- Check the inverter coolant level and condition — Inspect the inverter coolant reservoir, which is separate from the engine reservoir. Top up or replace coolant that is low, rusty or past its service life, using only the correct pink Toyota long-life coolant.
- Verify the inverter pump actually circulates coolant — With the system ready, watch the reservoir for flow and check for pump operation. A pump that is silent, intermittent or shows no flow is failing - the most common finding on a Prius.
- Rule out trapped air — Air in the loop mimics a failed pump. The Prius has no simple bleeder valve; the system is burped by running the car in inspection / diagnostic mode so the pump runs continuously until the air clears.
- Pro tip: a P0A93 that returns after a pump swap is almost always trapped air — If the code comes back soon after a new pump, re-bleed the loop properly in inspection mode before suspecting anything else.
- Common misdiagnosis: do not condemn the inverter first — The expensive mistake is blaming the inverter or HV system. P0A93 is a cooling-performance fault - confirm the cheap, likely causes (pump, air, coolant) before ever considering the inverter assembly.
Estimated repair costs
Typical US repair costs (parts & labour) for the faults behind P0A93. These are national-average estimates, not a quote— your actual price varies by region, shop labour rate, and your vehicle’s make, model and year. Figures reviewed 2026.
| Repair | Estimated cost (USD) |
|---|---|
| Diagnosis (scan + cooling-system inspection) | $75–$150 |
| Inverter coolant service + proper bleed | $90–$250 |
| Inverter coolant pump replaced (part + labour) | $300–$650 |
| Inverter assembly (rare, worst case) | $2,500–$6,000 |
Make & model notes
Toyota: The Prius is overwhelmingly the vehicle that sets P0A93, and the 2004-2009 Gen 2 is especially known for inverter-pump failure. Toyota TSB EG001-07 covers P0A93 with Information Code 346 caused by air trapped in the pump impeller. Use only the specified pink Toyota long-life coolant, and bleed the inverter loop in inspection mode - there is no conventional bleeder valve.
Other hybrids: P0A93 is a generic hybrid code and can also appear on the Camry Hybrid, Highlander Hybrid, Lexus hybrids and other makes that cool the inverter on a separate loop. The cause is the same class of fault - inadequate inverter cooling from a weak pump, trapped air, or low coolant.
FAQ
Can I drive with a P0A93 code?
It is best not to. P0A93 means the inverter is not being cooled properly, and an overheating inverter can be damaged. If the red triangle is on, drive only far enough to stop safely and have it looked at.
Is the red triangle the same as P0A93?
The red triangle is the master warning light - it tells you the hybrid system has logged a fault, but not which one. P0A93 is one specific fault that can turn it on; you need a scan tool to confirm the code behind the light.
How much does the Prius inverter coolant pump cost?
The pump itself is usually about $100-150. Done at a shop with coolant and the bleed, the job typically runs $300-650; it is a common DIY for under about $160 in parts.
Why did P0A93 come back after I replaced the pump?
Almost always trapped air. The Prius inverter loop has to be bled by running the car in inspection mode so the pump purges the air - if that step is skipped or rushed, the code returns even with a good new pump.